Ireland's commitment to collective security is pursued through the United Nations which has the primary role in the maintenance of international peace and security. The UN possesses no standing military forces of its own and relies on the provision of such resources by willing members. National sovereignty is a fundamental underlying principle of participation in the European security and defence policy. Participation in any specific operation by member states is decided on a case by case basis and in accordance with respective national decision making procedures. The provisions relating to participation of members of the Defence Forces in overseas missions are set out in the Defence (Amendment) Act 1960, as amended by the Defence (Amendment) Act 1993, which provides that a contingent of the Permanent Defence Force may be despatched for service outside the State, as part of a particular international United Nations force. Participation in an overseas operation requires UN authorisation, a specific Government decision and, where the level of participation is to exceed 12 members of the Defence Forces, the approval of Dáil Éireann.